The present invention relates to a device for selectively feeding threads in knitting machines or the like.
Conventional devices for selectively feeding threads in knitting machines in order to form patterns or lines on the resulting knitted fabric generally comprise a set of elements known as xe2x80x9cstripersxe2x80x9d arranged side by side and facing the needle bed or beds of the machine with an end at which there is a passage for the thread to be fed to the needles of the machine. Each striper is provided with an element for clamping and cutting the thread fed by the corresponding striper.
In most of the conventional devices, the thread clamping and cutting elements are arranged on the inner side of the needle bed of the machine and each striper is movable on command from the inner side of the needle bed toward the outer side in order to engage the thread clamped by the corresponding clamping and cutting element and arrange it transversely to the needle bed.
The thread thus arranged is then captured, in some kinds of machine, by a hook rigidly coupled to the needle beds and lowers said thread until it is deposited in the selvage retention clamps located at the beginning of the needle bed. Then the clamping and cutting element releases the thread, which is knitted in by the needles of the machine. In other kinds of machine, the thread dispensed by the striper is knitted in directly by the needles.
After knitting said thread and usually at the end of the needle bed, the striper is moved again toward the inside of the needle bed, toward the corresponding clamping and cutting element, which clamps and cuts the thread.
GB-2 196 026 discloses a striping device in a circular knitting machine wherein the stripers are movable and the cutting device performs cutting with a rotating movement.
U.S. Pat. No. 4 656 842 discloses a striping device wherein the stripers are also movable.
In other kinds of device, the stripers are fixed and are arranged on the outer side of the needle bed of the machine, while the corresponding clamping and cutting means are movable from the outside of the needle bed toward the inside and vice versa in order to arrange the thread transversely to the needle bed.
The actuation of the stripers or of the thread clamping and cutting elements in order to arrange the thread transversely to the needle bed of the machine is generally performed by way of cams applied to the needle bed, which is usually movable with respect to the stripers; said cams act on the stripers or on the clamping and cutting elements by way of levers and transmissions.
Accordingly, the patterns that can be achieved with conventional stripers are rather limited, since it is of course not possible to vary, during knitting, the arrangement and configuration of said cams in order to vary the thread or threads that are fed to the needles and to vary their feeding sequence.
The aim of the present invention is to solve the above problem, by providing a device for selectively feeding threads in knitting machines or the like which allows to produce patterns which are more complex and varied with respect to those that can be obtained with conventional devices.
Within the scope of this aim, an object of the invention is to provide a device which allows to vary, according to the requirements, the insertion and extraction points of the threads without requiring mechanical interventions on the machine.
Another object of the invention is to provide a device which allows to vary the insertion points of the threads row by row.
Another object of the invention is to provide a device which, besides providing greater operating flexibility, also allows to structurally simplify the machine on which it is installed.
This and other objects which will become better apparent hereinafter are achieved by a device for selectively feeding threads in knitting machines or the like, as claimed in claim 1.